Digital magnetic tape is commonly used for long term storage in computer systems. The low cost per bit stored, long term retention capability, and portability of magnetic tape cartridges has made magnetic tape the medium of choice for storing the large quantities of data produced by businesses such as banks, credit card companies, airlines, and the like. Automated tape libraries are often used to rapidly handle the number of tape cassettes required to hold large amounts of data. Such automated tape libraries typically include multiple tape units for accessing data on magnetic tapes and a robotic tape handling system for transferring tape cartridges between a tape unit and a cartridge storage location.
The large amounts of data to be stored are typically broken into volumes by host computers that process the data. A single tape cartridge is then used to hold the data volume. This may lead to waste as the magnetic tape stored in the cartridge may be capable of holding significantly more data than is contained in the volume. Also, tape management is typically controlled by a host computer. The host computer tracks location of cartridges, the volume on each cartridge, and the cartridge or cartridges being accessed by each tape unit.
One difficulty with current tape management systems is the overhead required of the host computer to manage the tape library. Another difficulty is that the tape management system within the host computer must be modified each time changes are made to the tape library. Yet another problem of current tape management systems implemented in host computers is the inability to manage tape cassettes containing multiple volumes.
A further difficulty with previous tape management systems becomes apparent when data must be manually put into or taken out of the computer system. For example, consider bringing data into the computer system from a separate computer system. If the tape cartridge is compatible with tape units in the automated tape library, the new tape must be manually introduced into the robotic tape handling system. The host computer must then be instructed to assign the new tape a volume identifier and process the tape into the tape library. If the new tape has a format incompatible with any tape unit in the automated tape system, a new tape unit must be connected to an open channel from the host computer. The host computer must then be directed to copy the information from the new tape cartridge onto a blank tape within the automated tape handling system. This may require writing specialized code for the host computer to access the new tape unit, read in the data, reformat the data for a cartridge type contained within the automated library system, and store the data on a blank tape cartridge.
What is needed is a tape library system that removes tape management functions from the host computer. This tape library system should handle multi-volume tapes to increase storage efficiency. The host computer should be presented with a virtual view of tape volumes and tape units so that extensive reprogramming of the host computer is not required. The tape management system should also allow for convenient copying of data to and from tape cartridges external to the automated tape library.